This invention relates to the reinforcement of articles of a kind having the general characteristic that reinforcing strand elements may be incorporated therein during the manufacture of such articles or of their constituent materials, for example by embedding such strand elements in the material if its manufacture involves a molding step, or by incorporating such elements between layers of a laminated material. The invention is thus applicable to the reinforcement of articles made of materials of the most varied kinds, such as for example concrete, plastics, rubber in either molded or laminated sheet form, and fabricated sheet material of the nature of hardboard, chipboard and laminated board. Articles of this kind are those hereinafter referred to as being of the kind described.
It is wellknown to reinforce such articles against the effects of tension by means of metal strands incorporated therein. In a simple form such strands can be metal ribbons or cylindrical wires. The reinforcing effect of a metal ribbon is however substantially increased if, as is also known, it is twisted either about itself or about an imaginary cylinder so that the edges thereof follow respective helical paths which are of equal diameter if the ribbon is twisted about itself or of diameters which differ by approximately the width of the ribbon if it is twisted about an imaginary cylinder. However, the increased reinforcing effect obtained by employing such a twisted metal ribbon is somewhat offset by the fact that a screw effect is thereby introduced when the reinforced material is in tension which tends in time to loosen the engagement between the reinforcing strand and the surrounding material. The present invention provides a reinforced article in which the latter disadvantage is overcome or substantially reduced.